For cutting blocks of marble, concrete, granite or the like, it is common to use either gang saws with horizontal or vertical reciprocating movement of the saw blade or blades. While these devices originally operated in such a manner that cutting was effected only when the saw blades moved either back or forth, and an idle stroke took place in the other direction, for reasons of economy one has in the meantime reverted to a method of cutting wherein the sawing takes place in both back and forth directions. Thus, for example, French Pat. No. 986,183 teaches a horizontal-gang in which the reciprocating movement of the saw frame provided with saw blades is overlapped by an up and down movement whereby the saw frame describes a movement similar to a double ellipse or a horizontal FIG. 8. The selected configuration is such as to allow each of the saw blades to cut the stone as they reciprocate from the center toward either end which is advantageous in that swarf formed during cutting, comprising cooling water, splintered off stone and abraded abrasive, is removed proceeding from the middle of the stone block towards its sides and accordingly, the wear is favorably affected.
A basic disadvantage of horizontal frame saws is, however, the limitation of the block sizes in all dimensions as well as the necessary relatively great length of the saw blades which means that the saw blade cross-section must be relatively large. Also, great tensional forces are required for fitting the saw blades in the saw frames which in their turn necessitate a very stable and therefore heavy construction of the frame.
These disadvantages are overcome by using vertical gang machines. However, the small number of hitherto known embodiments, such as that disclosed in the Belgian Pat. No. 530,257, have the disadvantage that during the up and down movement of the saw blades, the latter cut merely in one direction usually during the downward motion, and, as a consequence thereof, have an idle stroke which impairs the capacity of these machines.
In order to improve the capacity of gang saws for handling stones or the like, to reduce the wear occurring thereby and to obtain an unobjectionable cut, it is the object of the invention to combine the advantages of the various gang saw embodiments, yet without adopting their disadvantages.